1. Field of the Invention
This invention relates to a primer composition which assists in the adhesion of silicone elastomers to metallic and plastic substrates and accomplishes durable adhesion.
2. Prior Art
Various substrates of plastics such as epoxy resins, polycarbonate, PPS resin, PBT resin, ABS resins, and acrylic resins and metal materials are used in electric and electronic applications while silicone elastomers are bonded to such substrates through primer coatings. There is a desire to have a primer which accomplishes durable adhesion under any environmental conditions.
There are known a number of primer compositions for the substrates to which silicone elastomers are to be bonded. For example, JP-A 32030/1977 discloses a composition comprising a tetraorganotitanate, an epoxy group-bearing alkoxysilane, an aliphatic unsaturated bond-bearing organic silicon compound, a platinum compound, a polymer soluble in organic solvent, and an organic solvent. JP-B 2107/1986 corresponding to U.S. Pat. No. 4,332,844 discloses a composition comprising an alkoxy group-bearing organic silicon compound, an organic titanium compound, and a hydrosilyl group-bearing organic silicon compound. JP-A 25615/1994 corresponding to U.S. Pat. No. 5,326,844 discloses a composition comprising in admixture, an alkoxy-.alpha.-silyl ester and an alkoxysilane and/or an organometallic compound containing titanium or tin.
These primer compositions do not always achieve satisfactory adhesion. Some primer compositions provide satisfactory initial adhesion, but their long-term bond durability under rigorous conditions is insufficient. It is thus desired to develop a primer which forms a durable bond.